Process for producing semiconductor device

ABSTRACT

By conducting etching treatment using at least two steps with different compositions of gases for each step, and at least one step comprising using a gas capable of decomposing and vaporizing etching products in an etching apparatus continuously, semiconductor devices can be produced with high productivity, low contaminant and good reproducibility of treatment state.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for producing asemiconductor device, and more particularly, to a process for producinga semiconductor device characterized by effectively removing etchingproducts retained in a treating room.

[0002] With recent higher integration of semiconductor devices, circuitpatterns become finer and finer to make required processing dimensionalaccuracy severer. Under such circumstances, reproducibility of treatedstate becomes important.

[0003] For example, in an etching process wherein high processingaccuracy is required, in order to realize an anisotropic etching, thereis realized a process wherein etching is conducted while protecting sidewalls with a polymer produced by the etching. But the production ofpolymer changes depending on the amount of etching product retained in atreating room and wafer temperature. Thus, when the amount of reactionproducts retained in the treating room changes in each treatment,deposition state of side wall protective film causes deviation amongwafers, resulting in causing a problem of poor reproducibility ofetching shape. In a recent production process of semi-conductors, evenif a deviation of processing dimension is about 10 nm or less, theresometimes produce defective devices.

[0004] Further, an etching product retaining in the treating room formsa deposited film on inner wall of the etching apparatus, and peels offwhen the film thickness reaches to some extent to attach to wafersurface. Such peeled materials are called as contaminants and functionas masks at the time of etching processing to produce etching residues,which are one important cause for defective products.

[0005] In order to remove such etching products, for example,JP-A-5-144779 proposes to improve quality of the deposited film formedon inner wall of the etching apparatus, and JP-A-7-153751 proposes toconduct dry cleaning using plasma of mixed gases of oxygen gas andchlorine gas.

[0006] According to JP-A-5-144779, etching is conducted under conditionsfor improving the quality of film so as to make the deposited film oninner wall of etching apparatus hardly peeled off. According to thisreference, prevention of generation of contaminants may be effective dueto difficult peeling of the deposited film on the inner wall of theapparatus, but it is impossible to solve the problem of shift of etchingability by the deposited substance due to a premise of retaining thedeposited substance.

[0007] According to JP-A-7-153751, a step for plasma cleaning isprovided during etching treatment separated from an etching step, saidprocess being characterized by a material to be etched and an etchinggas, or a photo-resist made from a carbon compound which is a maskmaterial at the time of etching and a gas composition for removingso-called etching products generated by polymerization of etching gas.According to this process, by removing etching products at each intervalof treatment so as to make the reaction products retained in thetreating chamber not exceed a predetermined amount, the reproducibilityof etching shape is retained within a predetermined value and theformation of deposited film on inner wall of etching apparatus is to beprevented. But the step for plasma cleaning conducted separately fromthe etching step during etching treatment is a step not pertaining tothe production, and thus equal to “downtime” (a time when the apparatusis stopped) from the viewpoint of productivity. Therefore, this processconsiders cleaning effect for the etching products, but does notconsider productivity.

BRIEF SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide a process forproducing a semiconductor device overcoming the problems of prior artmentioned above, said process capable of attaining reproducibility oftreatment state and lowering of contaminants by removing reactionproducts retained in a treating room, while assuring productivity.

[0009] The present invention provides a process for producing asemiconductor device using a plasma treating apparatus comprising anetching treatment room, a substrate stage for placing a semiconductorsubstrate thereon installed in the etching treatment room, a plasmagenerating means for generating plasma in the etching treatment room,and a gas introducing means for introducing a treating gas into theetching treatment room,

[0010] said process comprising subjecting the semiconductor substrateplaced on the substrate stage to etching treatment using gases,

[0011] wherein the etching treatment comprises at least two steps usingdifferent gas compositions in each step in the same etching treatmentroom continuously, and at least one step comprises using a gas capableof decomposing and vaporizing compounds produced by the etchingtreatment.

[0012] The present invention also provides a process for producing asemiconductor device mentioned above, wherein the substrate stage has anelectrode for electrostatic adsorption and the decomposing and removingstep is used for further removing electrode voltage and charge stored inthe semiconductor substrate.

[0013] The present invention further provides a plasma etching treatmentapparatus used for the above-mentioned processes, and a semiconductordevice thus produced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic cross-sectional view of a semiconductorsubstrate for explaining Example 1 of the present invention.

[0015]FIG. 2 is a schematic view of a dry etching apparatus forexplaining Examples of the present invention.

[0016]FIG. 3 is a schematic cross-sectional view of a semiconductorsubstrate for explaining Example 2 of the present invention.

[0017]FIG. 4 is a schematic cross-sectional view of a semiconductorsubstrate for explaining Example 3 of the present invention.

[0018]FIG. 5 is a schematic cross-sectional view of a semiconductorsubstrate for explaining Example 4 of the present invention.

[0019]FIG. 6 is a output drawing of monitor for determining the etchingtime in the present invention.

[0020]FIG. 7 is a graph showing changes of monitor values with the timefor determining the etching time in the present invention.

[0021]FIG. 8 is a schematic cross-sectional view of a semiconductorsubstrate for explaining Example 5 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to solve the problems of the prior art mentioned above,the present invention provides:

[0023] (1) A process for producing a semiconductor device using a plasmatreating apparatus comprising an etching treatment room, a substratestage for placing a semiconductor substrate thereon installed in theetching treatment room, a plasma generating means for generating plasmain the etching treatment room, and a gas introducing means forintroducing a treating gas into the etching treatment room,

[0024] said process comprising subjecting the semiconductor substrateplaced on the substrate stage to etching treatment using gases,

[0025] wherein the etching treatment comprises at least two steps usingdifferent gas compositions in each step in the same etching treatmentroom continuously, and at least one step comprises using a gas capableof decomposing and vaporizing compounds produced by the etchingtreatment.

[0026] In the above process (1), in the case of etching Si and acompound including Si, there can be used as a gas capable of decomposingand vaporizing compounds produced by etching, for example, a gascontaining fluorine such as CF₄, CHF₃, C₄F₈, etc., or a mixture offluorine-containing gas and Ar or O₂, e.g. CF₄+Ar, etc.

[0027] In the case of etching Al and Al alloy, there can be used as agas capable of decomposing and vaporizing compounds produced by etching,for example, a gas containing oxygen such as O₂, etc.

[0028] Important thing in the present invention is that the treatinggases used in at least two steps should have different chemicalcompositions.

[0029] According to the present invention, the process (1) has thefollowing preferable embodiments.

[0030] (2) A process in above (1), wherein the substrate stage has anelectrode for electrostatic adsorption and the decomposing and removingstep is used for further removing electrode voltage and charge stored inthe semiconductor substrate.

[0031] (3) A process in above (1), wherein the semiconductor substratehas a film made of silicon or a compound containing silicon thereon, andthe gas capable of decomposing and vaporizing compounds retained in theetching treatment room is a gas containing fluorine.

[0032] (4) A process in above (1), wherein the semiconductor substratehas a film made of aluminum or a compound containing aluminum thereon,and the gas capable of decomposing and vaporizing compounds retained inthe etching treatment room is a gas containing oxygen.

[0033] (5) A process in above (1), wherein the semiconductor substratehas a film made of silicon or a compound containing silicon thereon andis held on the substrate stage by applying electrostatic adsorption, andthe treating gas in the form of plasma is a gas containing fluorine usedfor further removing electrode voltage and charge stored in thesemiconductor substrate.

[0034] (6) A process in above (1), wherein the semiconductor substratehas a film made of aluminum or a compound containing aluminum thereonand is held on the substrate stage by applying electrostatic adsorption,and the treating gas in the form of plasma is a gas containing oxygenused for further removing electrode voltage and charge stored in thesemiconductor substrate.

[0035] (7) A process in above (1), wherein the plasma treating apparatusfurther comprises a monitoring means for monitoring a retained amount ofthe etching products, and the decomposing and removing step is stoppedwhen the retained amount reaches a predetermined lower limit value.

[0036] (8) A process in above (2), wherein the decomposing and removingstep is stopped when a retained amount reaches a predetermined lowerlimit value using a monitoring means for monitoring the retained amountof the etching products.

[0037] (9) A process in above (1), wherein in the decomposing andremoving step the plasma generation position is set apart from thesemiconductor substrate.

[0038] The present invention further provides a plasma etching treatmentapparatus comprising

[0039] an etching treatment room,

[0040] a substrate stage for placing a semiconductor substrate thereoninstalled in the etching treatment room,

[0041] a plasma generating means for generating plasma in the etchingtreatment room,

[0042] a gas introducing means for introducing (a) a treating gas foretching and (b) a treating gas for decomposing and removing etchingproducts, into the etching treatment room, and

[0043] a monitoring means for monitoring a retained amount of etchingproducts.

[0044] Considering above, one of the features of the process of thepresent invention is to conduct etching treatment of a film or filmsdeposited on the substrate using gases in the form of plasma, saidetching treatment comprising at least two steps using different gascompositions in each step, and at least one step comprising using a gascapable of decomposing or vaporizing compounds produced by the etchingtreatment.

[0045] Another feature of the process of the present invention is toconduct etching treatment while holding a film deposited substrate on asubstrate stage by applying electrostatic adsorption, and after theetching treatment, there is provided a step for discharging chargesstored between the substrate stage and a wafer using a gas capable ofdecomposing and vaporizing compounds produced by the etching treatment.

[0046] A still further feature of the process of the present inventionis to determine a time necessary for the treatment using a gas capableof decomposing and vaporizing compounds produced by the etchingtreatment and retained in the etching apparatus, by monitoringdecomposed or vaporized etching products using plasma emission or massspectrometer, and setting the treating time by a time when the monitoredvalue reaches a lower limit value.

[0047] In the present invention, the gas capable of decomposing andvaporizing compounds retained in the etching apparatus includes a gascontaining fluorine such as CF₄, CHF₃, C₄F₈, etc., which may furthercontain an inert gas such as Ar, or O₂, a gas containing oxygen such asO₂, etc.

[0048] Gas compositions used for etching treatment and having differentcompositions means, for example, a combination of CF₄+Ar/HBr+O₂,Cl₂+BCl₃/O₂, or the like.

[0049] The semiconductor device obtained by the above-mentionedprocesses comprises a substrate, a laminate of at least two kinds ofmaterial layers formed on the substrate, and a pattern formed thereon byconducting etching treatment using a gas in the form of plasma, whereina material for forming at least one film on the substrate is a materialwhich is subjected to etching treatment using a gas capable ofdecomposing and vaporizing compounds generated at a time of conductingetching treatment of another film.

[0050] The present invention is illustrated by way of the followingExamples, but needless to say, the present invention is not limitedthereto.

EXAMPLE 1

[0051]FIG. 1 is a schematic cross-sectional view of a substrate forexplaining this Example 1, wherein numeral 1 denotes a siliconsubstrate, numeral 2 denotes a polysilicon film formed by chemical vapordeposition (CVD) on the substrate 1, and numeral 3 denotes a photoresisthaving openings on areas to be processed by etching treatment.

[0052]FIG. 2 is a schematic view of a dry etching apparatus forexplaining this Example. In FIG. 2, numeral 5 denotes an etchingtreatment room, numeral 6 denotes a waveguide for introducing amicrowave into the treatment room, numeral 8 denotes a gas introducingpipe, numeral 10 denotes a substrate stage for positioning a substrate,and numeral 14 denotes an exhaust vent for vacuum exhaust.

[0053] Etching treatment is conducted by introducing an etching gas fromthe gas introducing pipe 8 and adjusting the pressure to a predeterminedvalue. A microwave oscillated from a magnetron (not shown in thedrawing) is introduced into the treatment room 5 through the waveguide 6to produce plasma from the gas in the treatment room by resonance withthe magnetic field formed by a solenoid coil 7. Etching is conducted byapplying the plasma 4. In order to control processing shape according torecent etching treatment, there is employed an anisotropic etchingwherein ions are led into the substrate stage 10 by applying RF biasusing a high-frequency power source 12. Further, in order to make thetemperature in the substrate surface uniform and to make the etchingrate and etching shape in the substrate surface uniform, the substratestage 10 is formed so as to adsorb the substrate 1 by electrostaticadsorption. By adsorbing on the substrate stage 10, the thermalconductivity between the substrate stage 10 and the substrate 1 can beenhanced and the temperature control of the substrate can be conducted.For such purposes, there is provided a temperature control mechanism 11for the substrate stage 10 per se. In addition, there are devised showerholes 9 for uniformly introducing the etching gas into the treatmentroom 5. As mentioned above, in order to realize the anisotropic etchingwherein high processing accuracy is required, there is conducted aprocess wherein etching is proceeded while protecting the side wallswith a polymer produced by the etching. The production of the polymerwhich becomes a protective film is influenced by the amount of etchingproduct retained in the treatment room 5, and the degree of influencebecomes more sensitive, the finer the processing pattern becomes. Forexample, when the retained etching product is much, there is a tendencythat the processing shape, i.e. the size d shown in FIG. 1 becomeslarger due to too much attachment of the protective film. Since theamount of retained etching product in the treatment room 5 increaseswith an increase of the number of treated substrates, the processingshape sometimes changes even if the treatment is continued under thesame conditions. In up-to-date devices, the processing size is to become0.1 μm, so that even if this changing amount is about several nm,sometimes no sufficient properties can be obtained.

[0054] Features of this Example are that the etching treatment comprisesat least two steps using different gas compositions in each step, and atleast one step comprises using a gas capable of decomposing andvaporizing the etching products, or constituting the device using alaminated film etched by selecting the above-mentioned gas.

[0055] When the polysilicon film 2 shown in FIG. 1 is etched using aphotoresist as a mask, it is conventional to use a mixed gas of chlorine(Cl₂) and oxygen (O₂), or a mixed gas of hydrogen bromide (HBr) andoxygen (O₂), or a mixed gas of HBr, Cl₂ and O₂. In such a case, etchingproducts such are SiCl, SiH, SiO, SiBr, etc. are formed to attach toinner wall surface 5′ of the treatment room. Such attached productsinfluence etching properties.

[0056] In this Example, the etching was conducted by two steps, one ofwhich uses a mixed gas of CF₄ as a gas containing fluorine (F) and Ar,and another of which uses a mixed gas of hydrogen bromide (HBr) andoxygen (O₂).

[0057] In the step (1), the polysilicon 2 is etched by plasma of themixed gas of CF₄ and Ar. When Si is fluorinated, there is produced asubstance having a very high vapor pressure, which substance can beremoved after vaporization. In the step (2), using a mixed gas of HBrand O₂, anisotropic etching is conducted. That is, since no sufficientanisotropy is obtained by plasma etching in the mixed gas of CF₄+Ar, anisotropic etching is conducted by changing to the mixed gas of HBr+O₂.

[0058] According to this process, when the step (1) is conducted, theetching products generated in the etching treatment in the step (2) suchas SiCl, SiH, SiO, SiBr, etc. can also be removed.

[0059] According to the present inventors' experiments, the discharge ofthe mixed gas of CF₄ and Ar was sufficient for 10 seconds or 20 secondsat the longest to obtain the desired effects, although changed dependenton the film thickness of the polysilicon 2 and etching area.

[0060] Since influences of etching products generated by the previouswafer treatment can be removed by the above-mentioned etching treatment(two step etching), the etching processing with good reproducibilitybecomes possible. Further, since the etching products are notaccumulated on inner wall 5′ of the etching apparatus, low contaminantscan be realized. In addition, since the etching products generated inthe previous etching treatment can be removed, it is not necessary toconduct a cleaning step, which is required by prior art technique, apartfrom the etching treatment, resulting in obtaining an effect of notlowering productivity.

[0061] In the above, the mixed gas of CF₄ and Ar was used, but when CF₄alone or a mixed gas of CF₄+O₂ was used in place of CF₄+Ar, the sameeffects as mentioned above were obtained.

EXAMPLE 2

[0062]FIG. 3 is a schematic cross-sectional vies of a substrate forexplaining this Example. This Example is characterized by using a gascapable of decomposing and vaporizing compounds produced by etching forantistatic discharge of electrostatic adsorption in the case of applyingelectrostatic adsorption to the substrate stage.

[0063] As mentioned previously, in order to conduct etching treatmentrecently applied with good accuracy, it is essential that RF bias isapplied to the substrate stage 10 and the substrate 1 is adsorbed byelectrostatic adsorption. According to the electrostatic adsorption, adirect voltage is applied between the substrate 1 and the substratestage 10 to store the charge between the substrate 1 and the substratestage 10, and thus the substrate 1 is adsorbed. In order to remove theadsorption after the etching treatment, the voltage is cut. But, sincethe stored charge is not discharged immediately, it is necessary toconnect the substrate 1 and the substrate stage 10 to earth 15. Theearth from the substrate 1 in the case of electrostatic adsorption istaken from the inner wall surface while forming an earth line 16 viaplasma 4, so that it is necessary to discharge for destaticization for atime necessary to discharge the stored charge.

[0064] Here, the etching of the polysilicon film 2 was conducted by thestep (1) using a mixed gas of HBr and O₂, and after the etching, plasmaof a mixed gas of CF₄ and Ar was used for antistatic discharge in thestep (2). By the use of the plasma of mixed gas of CF4 and Ar, etchingproducts such as SiCl, SiH, SiO, SiBr, etc. generated by the etchingtreatment of the polysilicon 2 were removed.

[0065] In this antistatic discharge, in order to continue dischargeafter the end of etching, no RF bias is applied in order not to generateabnormal in processed shape. By conducting the antistatic discharge likethis, it becomes possible to remove influences of the etching productson the substrate treatment in the next step. Thus the same effects asobtained in Example 1 can be obtained.

[0066] In the above, the mixed gas of CF₄ and Ar was used, but when CF₄alone or a mixed gas of CF₄+O₂ was used in place of CF₄+Ar, the sameeffects as mentioned above were obtained.

EXAMPLE 3

[0067] This Example, wherein aluminum is subjected to etching treatment,is explained referring to FIG. 4 wherein numeral 1 denotes a siliconsubstrate, numerals 17, 18 and 19 denote a laminated film of titaniumnitride, aluminum alloy and titanium nitride formed on the substrate 1by sputtering, and numeral 3 is a photoresist having openings on areasto be processed by etching treatment.

[0068] In the case of etching a single film of aluminum alloy or alaminated film of titanium nitride/aluminum alloy/titanium nitride, itis conventional to conduct etching using a mixed gas of chlorine (Cl₂)and boron trichloride (BCl₃). According to the analysis by the presentinventors, it was made clear that the etching products retained in theapparatus were organic compounds derived from the photoresist, and amixture of aluminum and boron chlorides (BCl_(x)), and the proportion ofthe boron chlorides being particularly large. The residual depositcontaining aluminum can be removed by the plasma of a gas containing Cl₂as in the etching to produce aluminum trichloride (AlCl₃) having a highvapor pressure. But, since the residual products are a complicatedmixture of organic materials and polymers of etching gas and thechlorine forms a shape of covering the aluminum, it is impossible tovaporize using plasma of chlorine gas.

[0069] When oxygen gas (O₂) plasma is discharged in the step (1), theetching products comprising organic compounds derived from thephotoresist and the mixture of aluminum and born chlorides (BCl_(x)) arevaporized by bonding the organic compounds to oxygen and by subjectingthe mixture of aluminum and BCl_(x) to displacement reaction to vaporizechlorine. Further, the deposit in the form of BCl_(x) is removed byreleasing Cl molecule to produce BCl₃ and the Al contained in theresidual deposit is also removed partially by forming AlCl₃. Afterremoving the chlorine which covers aluminum by O₂ plasma whereinreplacement of chlorine by oxygen takes place by the step (1), whenplasma of a mixed gas of Cl₂ and BCl₃ is generated in the step (2),removal of the remaining aluminum compounds can be carried out. That is,by conducting plasma discharge of O₂ gas and plasma discharge of a mixedgas of Cl₂ and BCl₃ continuously, the etching products can be removedeffectively.

[0070] In this Example, etching of the laminated film of titaniumnitride 17, aluminum alloy 18 and titanium nitride 19 was conducted bytwo steps using the plasma of oxygen gas (O₂) and the plasma of mixedgas of Cl₂ and BCl₃. By the reactions mentioned above, the decompositionof organic compounds by the plasma of O₂ and the displacement reactionof chlorine by oxygen upon the mixture of aluminum and BCl_(x) takeplace. Then, etching of the laminated film of titanium nitride 17,aluminum alloy 18 and titanium nitride 19 and removal of the aluminumcompounds are conducted simultaneously, resulting in capable of removinginfluences of etching products generated by the previous wafertreatment. Particularly, during etching of the uppermost layer oftitanium nitride 17, removal of the aluminum compounds can be observed.But when a photoresist mask is used as a mask for etching, since thephotoresist mask 3 is isotropically etched by the plasma of O₂ gas to beshrunk as shown by 3′ (shrunk resist mask), it is necessary to make thephotoresist mask larger than the required size.

[0071] On one hand, according to this method, there arises an advantagethat it is possible to conduct processing under the minimum sizepossible for exposure to light by applying the shrinkage of thephotoresist mask. Thus, in addition to repoducibility of processingaccuracy, low contaminants and high productivity, there can be obtainedan etching method suitable for very fine processing. Further, in orderto make the rate of mask shrinkage minimum, it is desirable not to applyRF bias to the substrate stage 10 in the step using the plasma of O₂.

EXAMPLE 4

[0072]FIG. 5 is a schematic cross-sectional view for explaining anotherexample of etching treatment of aluminum. The film structure on thesubstrate is the same as Example 3 shown by FIG. 4.

[0073] In this Example, after the etching in the step (1), the plasma ofO₂ gas is used for antistatic discharge in the step (2). By using theplasma of O₂ gas for antistatic discharge after the end of etching, theetching products generated by etching treatment, organic materialsderived from the photoresist, and the mixture of aluminum and BCl_(x)are subjected to decomposition of the organic materials and thedisplacement reaction of chlorine by oxygen for the mixture of aluminumand BCl_(x). When the next substrate treatment is conducted under thisstate using the plasma of mixed gas of Cl₂ and BCl₃ for the etchingcorresponding to the step (1), it is possible to conduct etching of alaminated film of titanium nitride 17, aluminum alloy 18 and titaniumnitride 19 and removal of aluminum compounds simultaneously. That is, asin Example 3, since the plasma discharge using O₂ gas and the plasmadischarge using a mixed gas of Cl₂ and BCl₃ are conducted continuously,it is possible to remove the etching products effectively. In thisantistatic discharge, since discharge is continued after the end ofetching, RF bias is not applied to the substrate stage 10 so as not tocause abnormal in the processing shape. In this case, the photoresist isshrunk by isotropic etching by the plasma of O₂ gas as shown by 3′ as inthe case of Example 3 shown by FIG. 4, but there is almost no influenceof the wiring processing shape of the laminated film of titanium nitride17, aluminum alloy 18 and titanium nitride 19.

EXAMPLE 5

[0074] This Example explains how to determine the time necessary for thestep using the plasma of gas capable of decomposing and vaporizing thecompounds retained in the etching apparatus in Examples 1-4 shown inFIGS. 1 and 3-5. One of the features of the present invention is tomonitor the amount of attached substances on inner wall of the etchingapparatus using plasma emission or mass spectrometer and to fix the timewhen the monitored value or its differential value reaches an lowerlimit value. In this Example, the plasma emission is used for applyingto Example 3 shown by FIG. 4 of etching treatment of aluminum.

[0075]FIG. 6 shows plasma emission spectrum after 4 seconds from thebeginning of discharge during the step using the plasma of O₂ gas. FIG.7 shows changes of emission wavelength of Cl atom (754.7 nm) with thelapse of time from the beginning of discharge.

[0076] As explained in Example 3, by the use of plasma of O₂ gas, theetching products of organic compounds and the mixture of aluminum andBCl_(x) are subjected to decomposition of the organic compounds and thedisplacement reaction of chlorine by oxygen for the mixture of aluminumand BCl_(x). Since the plasma of oxygen gas is used, it is natural thatonly the emission of O is observed. But as shown in FIG. 6, Cl is alsoemitted in the plasma. This means that aluminum and the mixture ofBCl_(x) are retained. Further, as is clear from FIG. 7, the decay ofemission of Cl is observed. This means that the displacement reaction ofchlorine by oxygen takes place and Cl is reduced by discharge of O. Thatis, at the time of convergence of decay of Cl emission, it can be judgedthat the displacement reaction of chlorine by oxygen is finished.

[0077] While setting a lower limit of the decay value of Cl emission andregarding the time reaching the lower limit as the end of dischargingtime of 0 plasma, plasma discharge was conducted using a mixed gas ofCl₂ and BCl₃ continuously. As a result, etching shape with very goodreproducibility was obtained with a little generation of contaminants.When O plasma discharge is conducted exceeding necessity, the resistmask 3 is reduced, so that it is important to reduce the discharge timeto the minimum necessary time. As mentioned above, by monitoring theplasma emission, it is possible to set the minimum time necessary fordecomposing and vaporizing the etching products. When the process iscontrolled so as to stop the discharge automatically at the time of themonitored value reaching the set value and to enter to the next step, itis possible to conduct the etching treatment more effectively.

[0078] The position of plasma generation can be controlled by theposition of solenoid coil 7 shown in FIG. 2 and current value passingthrough the solenoid coil. By removing the position of plasma generationfrom the substrate, bad influences on the substrate during thedecomposing and removing step mentioned above can be controlled.

[0079] In this Example, the plasma emission was monitored, but the sameeffects can be obtained by employing any measuring means for detectingthe etching products, for example, monitoring of compositions in theretaining gas by mass spectrometer, e.g. monitoring changes of Clconcentration in the retaining gas with the lapse of time, and the likemethods. Further, in this Example, changes of emission signal with timewas monitored as it was, but it is possible to catch the degree ofchange, e.g. use of differential values of monitored values, with highsensitivity. In addition, this Example is explained using the etching ofaluminum, but in the case of etching of polysilicon, signals of F andsignals of SiF are to be monitored.

EXAMPLE 6

[0080]FIG. 8 shows another example of the film structure ofsemiconductor device of the present invention. In FIG. 8, numeral 1denotes a silicon substrate, numeral 20 denotes a polysilicon filmformed on the substrate 1 by CVD, numeral 21 denotes a silicon oxideSiO₂ film formed by CVD, and numeral 3 denotes a photoresist havingopenings on areas to be processed by etching treatment. In such a filmstructure, etching of the silicon oxide film 21 and etching of thepolysilicon film 21 are mostly conducted by using different etchingapparatuses or different treating rooms. But in the etching of the SiO₂film, when a gas containing fluorine such as CF₄ is used, it is possibleto conduct etching of both the silicon oxide film 21 and the polysiliconfilm 20 in the same treating room continuously, wherein the etchingproducts generated by the etching of the polysilicon film 20 can beremoved at the time of etching treatment of the SiO₂ film. As filmslaminated on polysilicon, there can be used those which can be etched bythe gas containing fluorine. It is also possible to use other films suchas silicon nitride film, reflection preventing films at the time ofexposure to light made from organic compounds. In the case of producinga semiconductor device by laminating two or more films with differentkinds of materials on a substrate, and by forming a pattern by dryetching, it is necessary to select a material for at least one filmwherein said material can be etched by a gas capable of decomposing andvaporizing compounds generated at a time of conducting etching treatmentof another film. By selecting such a material, it is possible todecompose etching products generated at the time of etching of anothermaterial at the time of etching such a material. By selecting such adevice structure, it is possible to produce. semiconductor deviceseasily and with little defect ones.

[0081] In the above Examples, the photoresist is used as a mask forprocessing, but it is possible to use so-called hard mask such as a maskmade of silicon oxide or silicon nitride with the same effects.

[0082] As explained above, since it is possible to remove influences ofthe etching products produced in the previous wafer treatmenteffectively during the etching treatment, it becomes possible to conductetching processing with good reproducibility. Further since the etchingproducts are not accumulated on inner walls of the apparatus, anapparatus with low contamination can be realized. In addition, comparingwith the conventional process containing a cleaning treatment apart fromthe etching treatment, high productivity can be attained.

[0083] According to the present invention, since influences of etchingproducts generated by previous wafer treatment can be removedeffectively, etching treatment with good reproducibility becomespossible. Further, since the etching products are not accumulated oninner wall of etching apparatus, low contaminant can be realized. Inaddition, it is not necessary to provide a cleaning treatment inaddition to the etching treatment contrary to prior art process, thedowntime can be removed to attain high productivity.

What is claimed is:
 1. A plasma etching treatment apparatus comprising:an etching treatment room; a substrate stage for placing a semiconductorsubstrate thereon installed in the etching treatment room; a plasmagenerating means for generating plasma in the etching treatment room; agas introducing means for introducing (a) a treating gas for etching and(b) a treating gas for decomposing and removing etching products, intothe etching treatment room; and a monitoring means for monitoring aretained amount of etching products.
 2. A plasma etching treatmentapparatus comprising: an etching treatment room; a substrate stage, forplacing a semiconductor substrate thereon, installed in the etchingtreatment room; a plasma generating means for generating plasma in theetching treatment room; and a gas introducing means for introducing atreating gas into the etching treatment room.